Making a Scene more Realistic
Take more time to study materials. Water is darker and has a gradient affected by the depth as it gets closer to the coast. (try to make tiling less obvious, combine different bumps or use smth procedural). The roughness from the sand/ ground is too shiny. The lighthouse has kind off poor shading it needs roughneess variation to push its quality.
Study as if you were painting check how values work in the pictures and try to match them in your materials. Use HDRI and photometric color 
Your shapes are too general there is no depth in terms on diferent scale, try not to skip details go from big shapes to the tiniest this can help you get a scale sensation and realism
Keep working on it, compare more photos, close ups from similar materials, study a lot. You can do this, build patience :)